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Faulty CPU or Motherboard

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June 28, 2011 9:04:37 PM

Hello all,

I recently purchased parts for a complete overhaul of my computer. New motherboard, new CPU, new RAM. Old parts kept were video card, hard disks, PSU, everything else.

When I start the computer, though, all the lights turn on and the fans start for less than a second, then the whole thing falls dead again. I've isolated the problem to either the motherboard or the CPU (Problem persists without board in case, without RAM, etc. The PSU worked in my previous build, and I'm sure it's powerful enough at 750W).

I just bought the motherboard and CPU 2 days ago, so I can still RMA either one of them, but I don't know which one to. Is there any way of me finding out? I have no other CPUs or motherboards compatible with either of the suspected problem parts.

Although I don't think it will be necessary for figuring out the problem, here are the specs of the build:
Core i5-2400
GIGABYTE GA-Z68X-UD3-B3
Crucial Ballistix Tracer 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10600) Desktop Memory w/ Green LEDs Model BL2KIT25664TG1337
Corsair TX-750W
CORSAIR CMPSU-750TX 750W ATX12V v2.2
Radeon HD 4650 w/ Zalman cooler
2 WD Velociraptor 80 GB
Rounded up to about 13 case fans, 3 of which are LED

To sum it up, I would just like to know if there is any way of testing whether it's the board or the CPU that needs to be RMA'd.

More about : faulty cpu motherboard

a b V Motherboard
June 28, 2011 9:31:06 PM

no, i cant think of any way to figure out which is the issue without an extra cpu or mobo. since they are both brand new, you might as well RMA both.

but have you tried running the system with just the CPU, MOBO, PSU, and RAM (using the built-in graphics)?? cause it could be the video card or psu.
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June 28, 2011 9:45:37 PM

r3xx3r said:
no, i cant think of any way to figure out which is the issue without an extra cpu or mobo. since they are both brand new, you might as well RMA both.

but have you tried running the system with just the CPU, MOBO, PSU, and RAM (using the built-in graphics)?? cause it could be the video card or psu.


I've tried every combination. Running with CPU, motherboard, and PSU alone is supposed to at least give warning beeps for no RAM installed, and there's no built in graphics, but that doesn't mean anything if it won't even POST. Video card and PSU are both pulled from a working unit anyway, and I specifically double-checked the PSU using the paperclip test.

What leads me to believe it's the motherboard is the lack of warning beeps on startup (I specifically installed a speaker into the case to test this). Nothing, although I've heard CPU problems can also cause this.
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a b B Homebuilt system
a b à CPUs
a c 80 V Motherboard
June 28, 2011 10:02:24 PM

DOA CPU's and motherboards do happen, but not very often. The problems you describe are far more often caused by user error. The checklist in my signature will help narrow down what's causing the problem.

I hope this doesn't come off wrong. I've just seen a lot of people RMA hardware that's working just fine.
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June 29, 2011 12:55:37 AM

shortstuff_mt said:
DOA CPU's and motherboards do happen, but not very often. The problems you describe are far more often caused by user error. The checklist in my signature will help narrow down what's causing the problem.

I hope this doesn't come off wrong. I've just seen a lot of people RMA hardware that's working just fine.


Checked everything in that list, despite having followed two similar guides already. The only part of all of the guides that I was a bit wary about was the motherboard standoffs, as I do not have the cardboard spacers that normally separate the standoffs from the board, but when I breadboarded the parts I had the same startup problem, so it couldn't be any problem with shorting between the board and backboard. :??: 
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a b B Homebuilt system
a b à CPUs
a b V Motherboard
June 29, 2011 1:48:21 AM

The first thing that you should do if you have not already done so is to clear the CMOS memory by using the link on the motherboard WITH THE POWER CORD DISCONECTED.
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June 29, 2011 1:50:04 AM

pjmelect said:
The first thing that you should do if you have not already done so is to clear the CMOS memory by using the link on the motherboard WITH THE POWER CORD DISCONECTED.


Tried that... same problem...
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June 29, 2011 2:03:01 AM

The only thing not mentioned in that guide, that I have seen a couple time. Some motherboards come from the factory with the bios reset jumper in the "on" position. A quick ready through the manual will tell you to remove the jumper, but who reads those things?

From the fans spinning for just a moment when the power is first applied then nothing it sounds like something is creating a short.

If you connected the PC speaker, and have gone through bread boarding the setup and still cannot get a post error beep from the system, then it could be one of three components. Power supply, Motherboard, CPU.

Sorry to increase your likely targets, but you should never rule out a bad power supply as incorrect voltages can cause issues with any other part in the system.
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June 29, 2011 2:29:14 AM

dalethepcman said:
The only thing not mentioned in that guide, that I have seen a couple time. Some motherboards come from the factory with the bios reset jumper in the "on" position. A quick ready through the manual will tell you to remove the jumper, but who reads those things?

From the fans spinning for just a moment when the power is first applied then nothing it sounds like something is creating a short.

If you connected the PC speaker, and have gone through bread boarding the setup and still cannot get a post error beep from the system, then it could be one of three components. Power supply, Motherboard, CPU.

Sorry to increase your likely targets, but you should never rule out a bad power supply as incorrect voltages can cause issues with any other part in the system.


The only reason I sincerely doubt it's my PSU is that it's a 750 Watt Corsair PSU that was working perfectly fine in my old setup. I pulled it directly out and put it in the new one, then after the problems started coming I tested it with the paper clip trick and the PSU worked fine.
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June 29, 2011 2:31:17 AM

Corsair does make great PSU's and I have yet to get a lemon. I guess if you paper clipped it already then you can rule it out.

Sorry for your loss =(
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June 29, 2011 2:33:05 AM

dalethepcman said:
Corsair does make great PSU's and I have yet to get a lemon. I guess if you paper clipped it already then you can rule it out.


Yeah, now I just need to figure out if it's the CPU or the motherboard...

dalethepcman said:
Sorry for your loss =(


What do you mean by that?
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a b B Homebuilt system
a b à CPUs
a b V Motherboard
June 29, 2011 9:04:06 AM

The problem can also be faulty or incompatible memory, try running with just one stick. Have you tried removing and refitting the processor?
It is very unlikely that the fault is the processor however new motherboards have a very high fault rate and as many as one in ten have a fault of one type or another.
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a c 122 B Homebuilt system
a c 172 à CPUs
a c 156 V Motherboard
June 29, 2011 1:03:24 PM

The paperclip trick can tell you if a PSU is bad (no activity at all). However, it can not tell you if it is good.

All it really tells you is that the PSU is capable of producing enough 12 volt power to run a fan. It does not tell you the condition of the 3.3 and 5 volt rails. It doesn't tell if the PSU can produce enough power to run a system. And it does not tell if you are getting the "PowerGood" control signal that the CPU needs to boot.
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June 29, 2011 2:35:42 PM

pjmelect said:
The problem can also be faulty or incompatible memory, try running with just one stick. Have you tried removing and refitting the processor?


I have tried it with just one stick (using both different sticks), two sticks, and no sticks at all to see if I get the "no RAM" beep error code. None worked. I doubt the memory is incompatible, as I purchased them from Newegg as a combo deal, meaning they were meant to be used together (I presume).

I have not tried refitting the processor, I guess that's worth a shot.

jsc said:
The paperclip trick can tell you if a PSU is bad (no activity at all). However, it can not tell you if it is good.

All it really tells you is that the PSU is capable of producing enough 12 volt power to run a fan. It does not tell you the condition of the 3.3 and 5 volt rails. It doesn't tell if the PSU can produce enough power to run a system. And it does not tell if you are getting the "PowerGood" control signal that the CPU needs to boot.


I still doubt that it was the PSU, though, as it is pulled directly from a working build.
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June 29, 2011 4:03:57 PM

Reseated the processor, same problem occurs...
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June 29, 2011 9:17:46 PM

Decided to just RMA the motherboard and hope for the best. If it comes back and the new one still has these problems, I'll RMA the processor. I've got 30 days, I think it'll happen in time.

Thanks for all the help, everyone.
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July 11, 2011 10:19:55 PM

As a note to anyone reading this in the future, I borrowed a working PSU from a friend and the thing started up perfectly fine. Apparently it is possible for a PSU to function powering a Pentium 4, where the same PSU will fail powering an i5. (This can't be a wattage problem; my PSU was 750W, and it did not work, whereas my friends was 650W and it did.)

Funny. Off to RMA'ing a 3-year-old piece of hardware...
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July 11, 2011 10:21:29 PM

Best answer selected by hobbenbobber.
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